. >> i want to goo mar raddatz with more on this. the suspects believed to be from chechnya, martha, originally at least in this region, the forme region o the soviet union, a hotbed of terrorists. >> reporter: we hate to speculate about motives because they had been in the united states for quite a while but as pierre pointed out whether they've gone back and forth we just don't know but they seem to have established a very permanent residence in cambridge, massachusetts. so what was going on between their homeland, if, in fact, it turns out to be chechnya and what was happening here, we just don't know. i mean, we are going through all social media, trying to look at who these men are, were in the case of the dead suspect to find out what motives they might have and i'm telling you, george, that is exactly what they are doing in all of government in the whole of government trying to figure out what a motive might be and trying to figure out if anyone else is here, if anyone else was involved in this, if any more attacks are imminen